A court has hit a beds-in-shed landlord with a record fine of £50,000 after he crammed 11 flats into two neighbouring properties and their gardens.

Abdul Rahim Khan, 77, will go to prison if he does not pay the fine within 12 months. He pleaded guilty to failing to comply with enforcement notices relating to two properties in Hounslow, west London.

The first notice required Khan to stop using one of the properties as three separate residential units, cease using an outbuilding as a residential unit, and demolish the outbuilding plus a single-storey extension that did not have planning permission.

The second notice required him to stop using the second, adjacent property as six self-contained residential units, cease using an outbuilding as a residential unit, and demolish the outbuilding and a single-storey extension that did not have planning permission.

Cllr Steve Curran, cabinet member for housing, planning and regeneration at Hounslow council, said: “This is the biggest fine we’ve ever had for this kind of case, and I’m delighted the courts have decided to send such a strong message to unscrupulous landlords.

“This was clearly a case of over-development and I hope this prosecution sends out a clear message that we won’t tolerate unscrupulous landlords flouting the planning rules.”

The enforcement notices were issued in August 2010. Khan appealed to the Planning Inspectorate, which upheld the notices. He then applied for a certificate of lawfulness for the developments, which was refused.

Officers from the council’s rogue landlord team visited the properties last summer after a tenant complained about the state of repair of the property, and found the enforcement notices had not been complied with.

After further warnings, legal proceedings began in February this year.

Khan pleaded guilty to the charges, and magistrates referred the case to Isleworth Crown Court last Friday.

Khan fined £25,000 for each charge of failing to comply with an enforcement notice plus costs of £2,677, to be paid in 12 months or he faces 18 months in jail.

The court heard that an official visit to the site last November confirmed the properties had been returned to single dwellings, but the illegal extensions, outbuildings and debris remained.